What would it take to make the most inhospitable planet for life?

There’s only one planet that we know of that hosts life – Earth. So what makes all the other planets so inhospitable? Which one is the worst? And would it be possible to make an even less hospitable world than any scientists have discovered so far? These are the questions that our hosts Leah Crane and Chelsea Whyte set out to answer.

This special episode of Dead Planets Society was recorded at New Scientist Live – New Scientist’s annual festival of ideas – in London on 8 October. Leah and Chelsea were joined by Lewis Dartnell, who is an astrobiologist at the University of Westminster in the UK, and Vincent Van Eylen, who studies exoplanets at University College London.

There are many candidates for the least-habitable known planet, and some are very close to home. For example, Mercury has one side that reaches temperatures of up to 430°C, while the other side stays around -180°C. Other terrible worlds are much more distant, such as the hot super-Jupiter called HAT-P-7b, which is more than 1000 light years from our solar system and only takes two Earth days to orbit its star – it’s so hot and dense in the atmosphere that it might rain sapphires. There are even planets that are slowly disintegrating and frigid worlds with no star at all where nothing ever changes.

But to make the worst of all possible worlds, our intrepid hosts and their guests decided to combine as many of these unpleasant properties as possible into one horrible planet full of intense radiation, acid rain, extraordinary winds, extreme temperatures and seas of lava. And they find that this awful world is surprisingly familiar…

Dead Planets Society is a podcast that takes outlandish ideas about how to tinker with the cosmos – from putting out the sun to causing a gravitational wave apocalypse – and subjects them to the laws of physics to see how they fare.

To listen, subscribe to New Scientist Weekly or visit our podcast page here.

Transcript

Vincent Van Eylen: We expect that the whole surface is basically molten, so it’s kind of like the floor is lava over the whole planet.

Chelsea Whyte: The floor is lava? That sounds really unpleasant to say the least. But today, that’s what we have in store for you: we’re dreaming up the most horrific planet we can.

Leah Crane: That’s right, it’s the worst of all possible worlds.

Chelsea Whyte: At Dead Planets Society, we imagine what it might be like if we were given cosmic powers to rearrange the university, and today we’re rearranging things for the worse.

Leah Crane: On purpose. We recently recorded an episode at New Scientist Live in London, and you get to hear it now. We were joined by Lewis Dartnell and Vincent Van Eylen and plenty of you lovely listeners.

Chelsea Whyte: Thank you so much for coming out to watch the show and for bringing us your fascinating questions.

Leah Crane: Right. So, for this episode we wanted to design the worst planet for life as we know it. And we started with what we already know exists.

Chelsea Whyte: Yeah. So, we explored the planets in our own solar system that we know are pretty awful for life, and what makes them so inhospitable, plus we talked about rogue planets and exoplanets that have particularly terrible conditions.

Leah Crane: Yeah, some truly horrendous places, just so bad. And then we talked about how we can combine these and what we can add to them to make the worst of all possible worlds. So, let’s get into it. Here’s Dead Planets Society from New Scientist Live. Enjoy!

Chelsea Whyte: Hi everybody. Thank you all for being here. We have with us Lewis Dartnell and Vincent Van Eylen. So, Lewis is an astrobiologist and a presenter and author based in London. And he is also a professor at the University of Westminster, and he’s appeared on numerous TV documentaries and radio shows, and he’s also written a book, one of five. The book is called Being Human: How our Biology Shaped World History. And Vincent is also here with us, he’s an astronomer and professor at University College London where he primarily studies exoplanets, which are worlds outside of our solar system. And he uses those enormous data sets that they have from NASA and ESA. that they get from the James Webb Space Telescope. to characterise exoplanets and their stars. So, Lewis, what are your worst planets?

Lewis Dartnell: I’m an astrobiologist, I spend most of my time thinking about where we could find life in our own solar system. And I don’t mean little green bug-eyed monsters – I mean hardy, single-celled bacteria. And I spend most of my time thinking about our next-door neighbour planet, Mars. And Mars we think has got a good chance of having life on its own surface, hardy, bacteria-like life. But it’s not exactly conducive to human life.

Chelsea Whyte: Yes, it’s a pretty miserable place for us.

Lewis Dartnell: So, for the sake of this thought experiment, let’s imagine that we are having this conversation on the surface of Mars and we accidentally pop outside for a stretch of our legs and a walk and we forget to put our spacesuit on, we would die exceedingly quickly. And one of the biggest problems with Mars is that its atmosphere is so very thin. It’s about six millibars, so about 6 per cent, 0.6 per cent of what the earth’s atmospheric pressure is. And we need the atmospheric pressure to basically stop our blood from boiling. I don’t know if anyone has seen “Total Recall”, the original film with Arnie, not the more recent adaptation which was awful. But it’s a scene where Arnie smashes his helmet of his space suit and his eyes start bulging and popping out of his skull. Wouldn’t quite be that bad, but it would still be a pretty unpleasant way to die. And maybe one of the last thoughts to be going through your mind as you feel the saliva boiling off your tongue would be seeing Earth as a star in Mars’s sky.

Chelsea Whyte: What a beautiful moment.

Lewis Dartnell: You would have that poetic moment to be able to see home as you perished on the surface of an alien world.

Chelsea Whyte: Yes, it sounds pretty awful. Pretty bad.

Leah Crane: Horrendous. I think people talk a lot about moving humanity to Mars. It’s pretty unpleasant as a place.

Lewis Dartnell: It is pretty hostile, yes.

Leah Crane: Even though it is potentially the best planet other than Earth for life.

Lewis Dartnell: Well, in many respects it’s the most Earth-like place we know about, it’s just not all that Earth-like. At least not now. It was much more Earth-like, we think, in its past, which is why we’re excited about the possibility of life there on a primordial Mars.

Chelsea Whyte: What about you, Leah?

Leah Crane: The planet I think is the worst also happens to be my least favourite planet, which is Mercury. It’s really close to the sun, and when we think about a planet being bad for life, a lot of the time we think about it either being very hot or very cold. Mercury is both. It is tidally locked, so one side always faces the sun, and that side, which we call the day side, is about 800° Fahrenheit, which is 430° Celsius, all the time – absolutely awful.

Chelsea Whyte: Yeah, too hot.

Leah Crane: Too hot.

Lewis Dartnell: That will give you sunburn very, very quickly.

Chelsea Whyte: Just a little too hot.

Leah Crane: A little too hot. Also, you’d get a lot of cancers from all of the radiation. And then there’s the other side which always faces away from the sun, which is -290° Fahrenheit or -180° Celsius, equally unpleasant.

Chelsea Whyte: Maybe worse. I don’t like cold more than I don’t like hot.

Leah Crane: Yes, potentially worse. And it’s got very little atmosphere, there’s very little going on on Mercury, it’s basically a big ball of iron with a little bit of rock on the outside that’s too hot and too cold. So, I don’t love it, and… There’s the very thin band that would be okay called the terminator, which is the area between the day side and the night side.

Chelsea Whyte: Would you have to just sort of run back and forth?

Lewis Dartnell: It’s also called the twilight zone. You could stand right on the edge of that shadow, the ring, the annulus around Mercury where the sun just hangs on the horizon forever.

Leah Crane: Yes. So, that would be pretty awesome, but if you took a couple of steps in the wrong direction-

Lewis Dartnell: Oops, freeze.

Chelsea Whyte: Yes, bad day.

Leah Crane: Oops. Yes.

Chelsea Whyte: I would say for me, in the solar system, Jupiter is my least favourite planet, I don’t like it. I don’t understand why everyone thinks it’s so beautiful.

Leah Crane: It’s the biggest and best one.

Chelsea Whyte: It’s not. We have this fight going back years. And, you know, a gas planet is pretty bad for life I think, it’s pretty noxious in there. And then I think once you get down under the gas, correct me if I’m wrong, but it’s, kind of, molten, right? Like, at some point it stops being gas and it starts being I don’t know what.

Lewis Dartnell: Or metallic hydrogen people talk about at the very core, the very centre of Jupiter where the pressure get so unbelievably high, even the molecular hydrogen has been pressed together into a, sort of, new state of matter to metallic hydrogen.

Chelsea Whyte: Yeah, so I don’t want to have a house there.

Lewis Dartnell: Don’t go there. You’d be dead long before you get there. You’d be dead in the upper cloud decks of Jupiter, don’t worry about that.

Chelsea Whyte: But then our Jupiter is not the only Jupiter is there, there are hot Jupiters.

Vincent Van Eylen: There are hot Jupiters.

Chelsea Whyte: Like, our Jupiter is terrible in my opinion, but a hot Jupe sounds bad.

Vincent Van Eylen: Yes, hot Jupiter is kind of like a Jupiter but much closer to the than the sun. So, it’s more like 2,000° on there pretty much everywhere.

Chelsea Whyte: Are there any, sort of, hot Jupiters you can think of that you’ve come across as you’ve studied exoplanets that are particularly horrific places?

Vincent Van Eylen: I would pick HAT-P-7b. So, that’s kind of a Jupiter-size planet. It’s roughly similar in size to Jupiter, but it has an orbit so much closer to its star that it gets around in about two days.

Chelsea Whyte: Oh, so it’s flying.

Vincent Van Eylen: So, there’s one good bit which is you’d have a birthday every two days. But other than that, there’s not much good about it if you want to live there, you know, it’s a ball of gas, it’s 2,000 plus degrees. There are winds that are several hundred or several thousand kilometres per hours going from the side facing the sun or the star to the back side. They probably have things like sapphire rain, it’s a pretty terrible place to be at.

Chelsea Whyte: Sapphire rain.

Lewis Dartnell: That doesn’t sound too terrible to me to be honest.

Chelsea Whyte: Kind of pretty, but.

Lewis Dartnell: If you had a net you could catch it as it fell.

Chelsea Whyte: But if you are just getting cut up by it.

Lewis Dartnell: If you’re dying while you’re fishing for the- yes, alright, fair enough.

Chelsea Whyte: Yeah, yeah, it might not be so great.

Leah Crane: What a way to go, though.

Chelsea Whyte: Well, I was also thinking about, you know, we’re talking about planets that are around a star, but there are rogue planets too, right, so these are planets that have been kicked out of their solar system, usually because another star comes by and disrupts an orbit or there is some orbital chaos with the planets and they just get booted out, like traffic jam. And I first thought these would be pretty rare, but I was looking it up and something like 38 per cent of solar systems have lost a planet in their lifetime. So, there’s lots of these rogue planets just kind of out there floating, you know, cold and frigid in the vastness of space. And even the ones with the thickest atmospheres would freeze and be pretty miserable, yeah?

Leah Crane: Eventually.

Lewis Dartnell: So, there has been some research that looks at rogue planets and they might still be able to have liquid water on the surface and be suitable for life, if they’re big enough with enough internal heat, like, sort of, heat that drives volcanos on earth. But also have a very, very thick atmosphere, they’ve got a pretty big, thick coat on that insulates them against that. But you’re right, most rogue planets are going to be far from the nearest star, far from their campfire of the sun and exceedingly cold, and again, not the sort of place you want to find yourself on.

Vincent Van Eylen: I think that would be pretty terrible because I think a rogue planet, and you’re right, there are probably many of them, it’s kind of like an Earth, but then there’s no more sun, it’s like permanent winter which sounds to me like probably the worst kind of thing to have.

Chelsea Whyte: Yeah, pitch black.

Leah Crane: I was about to say that every day would be the same, but there would be no such thing as days.

Chelsea Whyte: Every night.

Leah Crane: Always the same.

Lewis Dartnell: Everything is always the same, yes.

Leah Crane: Which sounds pretty awful. In addition to all the research that suggests that having things be different to each other sometimes is very important for life developing. Having tides and things.

Chelsea Whyte: Yeah, you need gradients, right?

Lewis Dartnell: So, I think those are pretty bad for life developing and also if you got dropped off there it would be kind of like eternal damnation a little bit, just the same all the time.

Chelsea Whyte: Unsustainable might be the way to put it. Yes.

Leah Crane: So cold. Awful.

Chelsea Whyte: Other kinds of exoplanets that we can think of that might be pretty miserable?

Vincent Van Eylen: Yes. So, when it comes to exoplanets, so planets around other stars, I think we know some 5000 by now.

Chelsea Whyte: That’s a lot.

Vincent Van Eylen: And we’ve done research on quite a few of them, and on some we know more than others. And of course one of the goals is really to find one that looks quite like the earth, right, we actually want to find Earth copies, Earth twins of some kind. And that’s been pretty hard. But we found plenty that are not like the earth and are probably pretty terrible. It was hard to narrow down to one planet that would be really terrible, so I picked three. One is HAT-P-7, the Jupiter that’s really hot. Another one is also very hot called Kepler-10b, but it’s not a Jupiter, it’s an Earth. So, it’s rocky, or it would be rocky if it wasn’t so hot. So, we expect that the whole surface is basically molten, so it’s kind of like the floor is lava over the whole planet.

Chelsea Whyte: Yes, that sounds bad.

Vincent Van Eylen: But that’s pretty bad, so that would be my second option. And the third one, K2-22b, is a planet that’s basically disintegrating. So, basically the planet is kind of slowly falling apart, there’s kind of like a tail of a comet, kind of, floating behind the planet, and so it’s basically at the end of its life and it’s being ripped apart. So, I would pick between being ripped apart, having a lava floor or the, kind of, sapphire winds. Whatever you think is worse.

Chelsea Whyte: These are good options, but I think being on a planet that’s being shredded while you’re on it seems like the scariest one for me.

Vincent Van Eylen: Perhaps, yes.

Leah Crane: But on the other hand, why choose?

Chelsea Whyte: Yeah.

Leah Crane: Here on Dead Planets Society, we have promised to make the worst possible world. So, I think we should talk about whether or not we can combine all of the things that make all these worlds awful into one mega awful planet.

Chelsea Whyte: Yeah, the worst of all possible worlds.

Leah Crane: So, some of them aren’t going to be feasible.

Lewis Dartnell: Well, combining very hot and very cold just makes a lukewarm planet, I guess, so you can’t combine all of the extremes.

Chelsea Whyte: Well, but we didn’t hear about Mercury. Because you have one side that’s-

Lewis Dartnell: If it’s tidally locked, exactly, it will have a very hot side and a very cold side, yes. But I think we talked about possibilities like a supernova, an exploding star going off nearby the planet, and that would make for a really bad day.

Chelsea Whyte: So, what would happen? What would that day be like?

Lewis Dartnell: Well, it would last for centuries or thousands of years. It would pummel the planet for a while, you would die quite quickly on the surface, but you would see an immense flash of light, which is what we see with supernovae in our galaxy and other galaxies as well. And with that would be a surge of radiation which would shred up your DNA, give you all the mutations and cancers that would end up killing you, but also that flood of radiation would start stripping away the ozone layer from a planet like Earth, and then if it’s not the radiation from the supernova that kills you, it would be the ultraviolet rays beating down from the star that you’re orbiting would kill you, and also it would make the worst kind of acid rain. It would make a lot of nitrogen dioxide in the atmosphere which would dissolve in the water and fall as super acidic rain. So, there would be many, many things all going wrong all at the same time if a star would explode too close to our Earth or another Earth-like planet.

Leah Crane: Let’s just be very clear that this isn’t going to happen any time soon.

Lewis Dartnell: It’s not about to happen.

Chelsea Whyte: But will it happen in the future, in the far, far future?

Lewis Dartnell: Well, as the sun orbits around the centre of our galaxy, the galaxy is swirling around, so we’re becoming closer and further away from other stars. So, 10,000 years, 100,000 years in the future, the night sky will look very different because all the stars have moved around. So, you might get a drive-by where a large massive star swings near to the earth and the solar system and through really bad, unlucky timing chooses that moment to pop off and explode when it’s nearby to us. There is a star that many of you will be familiar with, which is one of the shoulders of Orion, called Betelgeuse, and that is a super red giant star at the moment which will go supernova at some point in the future, but thankfully is very far away, as in far enough away that it won’t be a huge problem for the habitability of the earth when it does explode. It would be an awe-inspiring sight though, when that goes off in our sky.

Chelsea Whyte: Yeah. Well, so, here at Dead Planets Society we give ourselves magic powers to do whatever we want in the solar system, and so I’m wondering if we can put a planet, a perfectly nice one to begin with, around something that’s not a star. Like, what if a planet was orbiting a black hole, what would that be like? Would it be horrific? Would it be as terrible as I want it to be?

Vincent Van Eylen: That depends, I think. If you’re far enough away from a black hole, you could imagine you’re still in orbit around it and you’d be more or less fine, there would be no more star really.

Chelsea Whyte: No light, yes.

Vincent Van Eylen: But you’d be more or less fine. So, I’m not sure that’s the worst. I think something like a pulsar star that is beaming radiation the whole time. We actually know some planets around a pulsar, that sounds really terrible and it’s probably worse than a black hole, maybe counter-intuitively.

Chelsea Whyte: Because pulsar stars are spinning, right?

Vincent Van Eylen: Yes, so they’re spinning and they’re releasing high-energy radiation the whole time. So, you would be, kind of, blasted or beamed by radiation very regularly. So, that would be bad.

Leah Crane: It would be like sitting in front of a lighthouse.

Vincent Van Eylen: But all the meteors or asteroids around you, that seems pretty terrible as well, things falling from the sky all the time.

Chelsea Whyte: Yeah, a planet in an asteroid belt.

Vincent Van Eylen: I think that, so, there is a problem with that because currently according to the definition that the International Astronomical Union has made for what is a planet, you can’t have too asteroids or meteoroids in the area. That’s why Pluto is not a planet. But if you change that definition, and I suggest we do so we can have Pluto back.

Lewis Dartnell: You’re going to get off on a technicality.

Vincent Van Eylen: So, we can have Pluto back, but once you have that you could be in an asteroid belt as a planet and then you might have asteroids raining down often. I think it’s maybe interesting the first time, but it would get old after a while, and dinosaurs didn’t like it eventually, obviously, either.

Chelsea Whyte: Yeah, it was a pretty bad day here for them wasn’t it.

Lewis Dartnell: Good day for us in fairness though, for mammals, it gave us a bite of the cherry, it gave us a chance.

Leah Crane: It seems like some of these are really very similar to the earlier, the much earlier solar system. So, it’s funny to think that the worst planet, I don’t know, could have been Earth three billion years ago when there were lots of rocks and stuff coming in and things were a bit brighter and the surface was molten because of the collision that produced the moon. It seems like potentially, ages ago, Earth was one of the worst worlds.

Lewis Dartnell: And with no oxygen to breathe as well. So, you go back more than about two and half billion years in our past and you’d need a spacesuit to walk around even on the surface of the earth. Like, our Earth would have been an alien planet as far as we’re concerned if you back far enough before the atmosphere evolved.

Vincent Van Eylen: Yeah. I guess what’s terrible depends on your perspective, right? Terrible for us, it’s easy to find things, but it’s hard to know what’s terrible for everyone. I sometimes wonder if an alien were to look at the Earth, they might think it’s pretty terrible. They might say, ‘It seems to spin every 24 hours, day, night cycles, every 24 hours you go from warm to cold, you’d never to be able to survive on there.’

Lewis Dartnell: Yes, there’s no oceans of ammonia that you can drink.

Vincent Van Eylen: Exactly. Yes.

Chelsea Whyte: But there are some other non-earth situations that could be pretty bad, right? So, what if there was a planet that was in just a very busy area of space, like a stellar cluster? I’m curious because space is so big and so vast and I always forget how much of it is out there. How smushed together could a planet be? How busy a neighbourhood could it live in and still hang together as a planet?

Lewis Dartnell: Well, the solar system did form as part of a stellar cluster and then they all drifted off and went their own way. And there have been research projects looking at trying to identify the sun’s siblings, trying to find stars with very similar spectral characteristics, and they might be born as part of the same family. But one of the problems for a planet with life on it being part of a star cluster is that some of those stellar siblings will be bigger, more massive, burn through their nuclear fuel much more quickly and then explode. So, we’ve talked about supernovae already, you really as a life-bearing planet probably don’t want to be part of a star cluster because some of your star’s siblings might live fast, die young, blow up and then wipe out all life on your world, and that would be a bummer.

Chelsea Whyte: Yeah, it would.

Leah Crane: Or turn you into a rogue planet, just yeet you out of your system gravitationally.

Vincent Van Eylen: It doesn’t have to be nearby stars, alright. So, when we form planets, we think the sun and the planets form at the same time, and initially that’s, sort of, gas and dust when you have planets, so that where we think there may have formed more than eight or nine if you like Pluto, I do.

Chelsea Whyte: I do, too.

Vincent Van Eylen: Then you have more of them and some of them haven’t survived or have been but are now just free-floating planets, they probably formed around a star but were kicked out. And some probably crashed into each other, right, we think the moon is a result of a crash and that formed Earth and moon. So, it’s a pretty violent process, forming planets, and so you end up with some that live and some that don’t. Some might have crashed onto their stars and, kind of, been swallowed by the stars and some have been ejected to space and in the internal darkness.

Chelsea Whyte: I mean, getting back to the worst of all world, being swallowed by a star sounds like a pretty bad day for a planet too, right?

Vincent Van Eylen: It probably is, yes.

Lewis Dartnell: There’s something very neat you could do with rogue planets because they’re ejected from star systems by the gravitational interaction or the other planet swirling around. But we’ve also seen stars and probably planets as well being ejected from black holes, the black hole in the centre of the galaxy. So, if you wanted to journey from one galaxy to another galaxy, one way of doing that might be to engineer, you know, for some super advanced civilisation to engineer the gravitational interactions to eject a planet in the right direction towards the next galaxy, so you can then ride it and have all the resources and the things you need to keep yourself going for the long, long voyage.

Chelsea Whyte: That would be incredible.

Lewis Dartnell: Rather than trying to build a spaceship, you would just turn your planet into a spaceship and fling it in the right direction.

Chelsea Whyte: Ping pong through the cosmos.

Lewis Dartnell: Exactly, yes. So, sort of, sci-fi type scenario that we might be attempting as a species in the far future.

Chelsea Whyte: I like that. Well, so, thinking about all of these terrible, terrible things that we’ve talked about, can several of them exist together on one planet? Like, what doesn’t negate each other? Would the worst planet have a star or not?

Lewis Dartnell: Sure.

Leah Crane: I think it should have a star. I think that the other ones are, like, cold, but there’s not as much going on.

Chelsea Whyte: Yes, I feel like a planet that’s got the molten surface is very close to-

Lewis Dartnell: That sounds worse than a cold planet.

Chelsea Whyte: Right?

Lewis Dartnell: So, you’d rather go to Antarctica for a holiday than go to somewhere super hot.

Vincent Van Eylen: Yes, this is a question of whether you’re a winter or a summer person. Do you think days are too hot or do you think winter is the most miserable?

Chelsea Whyte: Frankly I’m more in the middle, I like a mild temperature.

Leah Crane: I’m a winter person.

Chelsea Whyte: But I think hot sounds worse.

Lewis Dartnell: Alright. So, hot worlds, so we’ll have your the floor is lava molten surface planet.

Chelsea Whyte: The floor is lava, okay.

Lewis Dartnell: Orbiting too closely to its star.

Chelsea Whyte: And maybe the star is going to explore or have a bad day.

Lewis Dartnell: Yep. That would do it.

Leah Crane: Could we do a half and half? Could it be possible to have a planet where it’s got a night side and only the day side is so hot that it’s molten?

Vincent Van Eylen: Probably.

Chelsea Whyte: At some point do you get too close?

Vincent Van Eylen: Most of these planets have a permanent day side because they’re like the moon, you see the same side all the time, so if you’re living on the day side, you’d see the sun the whole time, and if you’re on the back side, you actually wouldn’t see the sun at all. So, in that sense, maybe even if you’re close, and it might still be pretty warm, you wouldn’t actually see the sun at all, so it would still be dark.

Chelsea Whyte: Okay, best of both words.

Leah Crane: So, we want hot and cold.

Chelsea Whyte: Okay.

Lewis Dartnell: It would also be really stormy if you’ve got one side of your planet which is incredibly hot on the sun side and the far side where it’s living in eternal night time and the planet had an atmosphere, you would have the most incredible storms washing from the day side to the night side.

Chelsea Whyte: Yes, that sounds terrible.

Lewis Dartnell: So, you can have that as well. You can have a stormy hot planet.

Chelsea Whyte: Okay. And can we get that sapphire rain in there?

Vincent Van Eylen: I think yeah, that should not be a big problem, or meteorites falling-

Chelsea Whyte: If we are to live in this terrible wind on this terrible planet, I want the sapphire rain.

Lewis Dartnell: You want have a heavy bombardment of asteroids as well, fair enough, you can have that.

Leah Crane: I feel like we’re at a cosmic restaurant just ordering everything.

Lewis Dartnell: Everything on the menu.

Chelsea Whyte: Exactly.

Leah Crane: All the worst things on the menu.

Chelsea Whyte: Exactly. But I do think, to me, that’s the worst, right. Hot, tidally locked, terrible winds, sapphire rain, but the one thing that’s worse than that is engulfed. Like, I think this one exists.

Lewis Dartnell: Plunging into the star would arguably be worse than all of that. I would agree with you I think, yes. As your star reaches the end of its natural lifetime and expands out as a red giant, that will be the end of days but also the worst day, you’d be saving the worst until last in terms of the planet’s history.

Vincent Van Eylen: Yeah, I think that’s a good way to get engulfed as well. If you wait for your star to eventually grow in size, we know this will happen to the sun over time, it will grow, you, kind of, slowly see it grow until it eventually comes towards you and engulfs you. So, you’d see it happening over a long time, you’d see the star come closer and closer until- it’s not you falling onto the star, it’s the star coming towards you and eventually you’ll be engulfed.

Chelsea Whyte: But you’re right, the terror of watching it come at you is the worst part of that, not even being on the worst of all worlds.

Vincent Van Eylen: You, sort of, know how many years you have left, yes.

Leah Crane: I mean, it would be over the course of generations, right? You wouldn’t be seeing it get closer.

Lewis Dartnell: It would take a while.

Chelsea Whyte: I don’t know, come on.

Leah Crane: I mean, I wish. But that is going to happen here, right? All the inner planets will be engulfed by the sun.

Vincent Van Eylen: Yes. The sun will grow in size and then the closer you are the more in trouble you are likely to be.

Leah Crane: So, I’m just saying, I don’t have a vendetta, but this sounds a little bit like Mercury. Just a little bit worse, but mostly Mercury.

Chelsea Whyte: It does sound a little bit like Mercury. Very close, tidally locked. It doesn’t have that sapphire rain.

Leah Crane: It doesn’t. It doesn’t have an atmosphere, so we’d have to give Mercury an atmosphere.

Chelsea Whyte: And then we’ve made the worst of all worlds.

Leah Crane: Mercury Two.

Chelsea Whyte: We already did it.

Chelsea Whyte: It’s almost unbelievable that the worst planet we can imagine is very much like one we have right in our own solar system.

Leah Crane: It’s not unbelievable, I knew it from the beginning, and now it’s confirmed that Mercury is the worst.

Chelsea Whyte: I suppose it is. I wonder how much less worse it would get if we took one of our listener’s suggestions. James from London wrote in to ask what would happen if Mercury and Neptune switched places, how would that affect the solar system? I’m guessing there would be some orbital dynamic chaos for sure.

Leah Crane: And maybe Neptune would become another Mercury. We’ll have to investigate that one further. Thanks James. And thanks to everyone who joined us in London at New Scientist Live. Talk to you next time.

Chelsea Whyte: Bye.